Vault protection system

ABSTRACT

An electrical protection system of the acoustic type for bank vaults and like structures which provides means for collecting the sound from numerous points whereby adequate protection is provided for vaults of building block construction at far less expense than is possible under the prior art. The invention also permits operation at higher sensitivity levels while maintaining normal stability when used in conjunction with vaults of monolithic construction.

United States Patent [72] Inventor Charles D. O"

East Brunswick, NJ. [21] Appl. No. 812,689 [22] Filed Apr. 2, 1969 [45]Patented Nov. 2, 1971 [73] Assignee American District Telegraph CompanyJersey City, NJ.

[54] VAULT PROTECTION SYSTEM 10 Claims, 7 Drawing Figs.

[52] U.S.CI 340/261, 179/115.5, 109/38 [51] Int. Cl (30% 13/16 [50]Field of Search 340/261, 273;179/110.1,113,114,115,115.5;109/38,42

[56] References Cited UNITED STATES PATENTS 640,273 1/1900 Coleman340/261 UX TO INPUT OF ELECTRONIC DETECTING AND ALARM DEVICE 1,762,9736/1930 Frederick 340/261 3,366,749 l/l968 Ries 179/1 15.5 3,423,543l/l969 Kompanek 179/1 10.1 3,487,396 12/1969 Perelman 340/261 PrimaryExaminer-John W. Caldwell Assistant Examiner-Perry Palan AltorneyCharIesB. Smith ABSTRACT: An electrical protection system of the acoustic typefor bank vaults and like structures which provides means for collectingthe sound from numerous points whereby adequate protection is providedfor vaults of building block construction at far less expense than ispossible under the prior art. The invention also permits operation athigher sensitivity levels while maintaining normal stability when usedin conjunction with vaults of monolithic construction.

PATENTEDnuvz I97! 3,618,062

saw 1 or 3 FIGI.

DEVICE DETECTING AND ALARM TO INPUT OF ELECTRONIC F|G.|A.

inui? FIGZ.

VAULT PROTECTION SYSTEM BACKGROUND OF THE INVENTION signal at selectedremote locations that the protected area is under attack. An earlyexample of such a system is found in U.S. Pat. No. 1,192,312 issued July25, 1916, to R.M. Hopkins and J. F. D. Hoge.

The noises produced during an attack depend primarily upon the nature ofthe tools employed for the purpose and these have varied widely as moreand more sophisticated tools and techniques have become generallyavailable. Thus, for instance, the simple sledge hammer attack of yearspast may now be replaced by the use of a portable core drill withdiamond cutters or a hydraulic jack may be employed to push down aportion of the vault wall. In the case of vaults constructed of buildingblocks joined together with mortar, the attack may consist of thescraping away of the mortar with a pointed tool.

The noises produced during an attack upon a vault are transmitted boththrough the air and through the material of the vault walls, floor andceiling. The earlier vault protection system, of which the previouslymentioned US. Pat. No. 1,192,312 is representative, depended primarilyupon the detection of airborne sounds; More recently, however, it hasbeen found that superior performance is obtained from protection systemsdesigned to respond primarily to the sound energy within the vaultstructure itself because this mode of operation greatly inhibits theincidence of false alarms caused by adjacent but innocuous sources ofloud noises such as jet aircraft and heavy vehicular traffic. An exampleof such a system is found in U.S. Pat. No. 3,134,970 issued May 26, I964to L. H. Kelly and A. C. LaMartina, Jr.

It is evident that protection systems designed to respond to the noiseswithin the vault structure are most satisfactorily applied to monolithicvaults, i.e., vaults constructed of poured concrete, as continuousmaterial provides the best sound transmission path. Even so, vaults thusconstructed must have occasional discontinuities in the form ofexpansion joints which interrupt the sound transmission paths andrequire the installation of additional microphones to ensure adequateprotection. The additional installation expense of a few extramicrophones is not of critical importance in the case of monolithicvaults. But when the vault is constructed of preformed building blocksmortared together, the presence of so many discontinuities in thestructure makes the cost of providing enough microphones to ensureadequate protection for the entire structure a very serious economicproblem.

The principal object of the present invention therefore has been theprovision of a novel and improved acoustic protec-.

tion system for vaults and. like structures which overcomes certaindisadvantages of the prior art.

More particularly, it has been an object of the invention to provide aprotection system for vaults of block construction that is both economicto install and reliable in operation.

In protection systems of all types for both fire and burglar alarmpurposes, it is necessary to strike a workable balance betweensensitivity and stability. Almost regardless of the phenomenon beingmonitored, be it noise, heat or electrical signals, there are availabletoday sensing devices of such sensitivity as to make possible thedetection of very small occurrences of the phenomenon of interest.Unfortunately, it is equally true that it is rare that the phenomenoncan be observed against an absolutely neutral background. Almost alwaysthere will be present extraneous ambient conditions which so closelyresemble the desired phenomenon that the detecting device will respondthereto and produce an unwanted or false signal. It is now customary tospeak of this problem broadly as the signal-to-noise ratio" andstrenuous efforts are being made in all the technical disciplines toimprove thereon. When the ratio is poor, the incidence of false signalsis high and the systems therefore lacks stability.

Obviously the signal-to-noise ratio" is important in the protection ofvaults against attack and much research has been done to determine theparticular characteristics of the noises produced by genuine attacks sothat innocuous sounds may be discarded by techniques involvingfrequency, amplitude and time duration discrimination. Any measures thatwill improve the signal-to-noise ratio will permit operation of theprotection system at a higher sensitivity while holding the stability ofthe system at an acceptable level and therefore result in improvedprotection for the vault.

Accordingly, it has been another object of the invention to provide avault protection system having improved sensitivitystabilitycharacteristics.

Other and further objects, features and advantages of the inyention willbe apparent from the following description of the invention.

SUMMARY OF THE INVENTION The invention comprises the provision ofspecific means for the collection of attack noises existing within avault structure and the efficient transmission thereof to one or moremicrophones of a vault protection system. The microphones of theprotection system are connected to metallic strips which are in turnconnected to the interior surfaces of the vault to be protected bysuitable anchoring fasteners. Each fastener serves as a sound collectingpoint for noises within the structure and transfers that noise to themetallic strip whereby it is effectively and efficiently transmitted tothe microphones. The low cost of the fasteners and metal stripping ascontrasted to the expense of providing enough microphones to adequatelyprotect a block-constructed vault makes possible the protection of suchvaults at reasonable expense. Furthermore, the plurality of soundcollection points coupled with a highly efficient means of transmittingsound to the microphones results in the receipt of a stronger signalunder attack conditions and an improved "signal-to-noise ratio wherebythe protection system may be operated at a higher sensitivity level thanwould otherwise be possible at a given stability rating.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described ingreater detail with reference to the appended drawings in which:

FIG. 1 is a perspective view of a contact microphone and mounting platesuitable for use in the system of the invention;

FIG. 1A is a cross-sectional view of the microphone of FIG.

FIG. 2 is a cutaway front view illustrating an embodiment of theinvention in which the microphones and strips are installed on a wallofa vault;

FIG. 2A is a front view of a completed microphone installation in theembodiment ofFIG. 2;

FIG. 2B is a cross-sectional view of FIG. 2;

FIG. 3 is a cross-sectional view of an alternate arrangement forinstalling microphones and strips on a wall of a vault;.and

FIG. 4 is a diagram indicating a typical approximate spacing and layoutof the microphones employed to protect a typical vault.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. I. there isshown a microphone 10 secured to a mounting plate II. A microphonesuitable for the purposes of the present invention may be of the contacttype,

taken along the line 28-28 which might, for example, be responsive to afrequency range of about 7,000 to 50,000 cycles per second. Themicrophone may comprise an aluminum disk 12 approximately 1% inches indiameter, about 3/64 inch thick and provided with three radial slots toreceive mounting screws 13 which serve the microphone to the mountingplate 1 1.

As shown in FIG. 1A, a ceramic composition transducer element 10A, whichis desirably of the lead zirconate titanate type, is adhesively affixedto the top surface of disk 12 by an electrically insulating adhesive10B, e.g., an epoxy cement, which will transmit vibrations from the diskto the transducer element. An aluminum housing 14 which may bethree-eighths inch high and seven-eighths inch in diameter is affixed tothe top surface of disk 12, e.g., by an epoxy adhesive MA. A shieldedcable 15 having conductors l6 and 17 connected to the respectiveterminals of the transducer element is brought out through a slot 18provided in housing 14. The spaces between the cable 15 and slot 18 aswell as the joint between housing 14 and disk 12 are filled with theepoxy cement to form a watertight assembly.

The mounting plate 11 may be conveniently formed from one-eighth inchthick steel strip and is provided with a clamp 19, held by screw 20, tosecure the cable 15. The mounting plate is also provided with a pair ofslots 21 located at the opposite ends thereof and a pair of tapped holes22, located adjacent each slot, whose purpose will be made apparenthereinafter.

Microphone 10 may be connected in parallel with the other microphones ofthe protective system via the conductors 16 and 17 and thence to theinput of a suitable electronic detecting and alarm device which may beof the type described in the previously mentioned US. Pat. No. 3,134,970wherein the detected sounds of an attack upon a protected vault areconverted into a suitable warning signal. Each of the microphones shouldbe mounted so as to be in close vibratory contact with a wall of thestructure being protected. That is to say, the physical coupling betweenthe wall and a microphone should readily transmit sound energy from thewall to the microphone.

It will be evident from the foregoing that the general import of thepresent invention is to provide sound collecting means and transmissionpaths so that more economical and efficient use may be made of themicrophone unit described above or of similar microphone units. Thoseskilled in the art will recognize that the basic components foraccomplishing this end as described hereinafter may be combined in avariety of combinations and configurations and that the followingembodiments of the invention are intended as illustrative of theinvention rather than as limitations thereof.

One arrangement for mounting the microphone units is shown in FIGS. 2and 2A. Referring first to FIG. 2, the mounting plate 11 which is heldin intimate contact with microphone 10 by the mounting screws 13 isfirmly secured to the surface of the vault wall by two screw fasteners23 acting in the slots 21 of the mounting plate 11.

Careful choice must be made of the type of fastener to be employed at 23and all other locations where connection is made to the surface of theprotected structure because these elements are the primary means wherebysounds are transferred from the structure to the transmission paths tothe microphone. Therefore the lead (or plastic) type of expansion plugshould be avoided because the soft material will impede the transfer ofsound. Best results are obtained through the use of expansion shieldsmade of a harder metal such as malleable iron. ln the case of hollowwalls, steel toggle (butterfly) bolts may be successfully employed.

immediately adjacent each end of the mounting plate 11 there areinstalled steel channel (U shaped) members 24 whose length is determinedby the requirements of the particular installation and the ease ofshipping and handling the material. Ten foot sections have been foundto.be generally most convenient. These members 24 are carefullyfastened, with the hollow side toward the wall, by fasteners 23' whichhave the same sound transmission characteristics of the fasteners 23employed with mounting plate 11. If necessary, additional channelmembers 24 are butted to the channel members 24 to complete the desiredlength of run. It should be noted that no particular efi'ort need bemade to obtain an intimate, metal-to-metal joining between channelmembers 24 and 24' or between channel member 24 and mounting plate 11other than to present a neat appearance. The reasons therefor are thatupon a wall of normally rough texture, such a joining is virtuallyimpossible and it is not necessary as it has been found that soundenergy is adequately transmitted via the wall between adjacent fastenerswherever joints occur. Thus the path for sounds from channels 24' is viathe end fastener 23' thereof, the wall to the adjacent end fastener 23'of channel 24, thence to the other end fastener of channel 24, the wallagain to fastener 23 of mounting plate 11 and therethrough to themicrophone 10. As a practical example, if the mounting plate 11 were 1/4 inches in width, the channel member 24 might conveniently have aninside dimension of 1 5/16 inches. The joints between channel members 24and 24' might range from actual contact at a point to a gap of perhaps1/32 inch.

To finish off the installation for a neat appearance and to provide adegree of mechanical protection for the microphone 10, a cover 25 may beprovided as shown in FIG. 2A. Cover 25 has been omitted from FIG. 2. Thecover 25 is easily constructed of a short length of channel materialwhose inside dimensions are just sufficient to fit over the channels 24and is held in position by two screws 26 which engage the tapped holes22 in mounting plate 11. The cover 25 is not a part of the soundtransmission path.

The sound conducting strip need not necessarily be of channel shape asequally satisfactory sound transmission would be obtained from othershapes, e.g., strips of rectangular cross section. it is, however,important that a hard metal be employed since the softer materials,e.g., aluminum, do not pos sess as good sound transmittingcharacteristics. The channel shape is generally considered the mostsatisfactory as the cable 15 is concealed for better appearance and isalso protected from mechanical damage. Ordinary steel conduit, so longas it is properly anchored to the vault wall so as to receive soundenergy therefrom, can be used in the invention. ln such case the conduitserves as the sound transmission path to the microphones and thefasteners which attach the conduit to the wall serve as the soundcollecting points.

An alternate form of installation which eliminates the need for thecovers 25 is shown in FIG. 3. Here the microphone and mounting plateunit are secured to the inside of the channel member 24 by means of twoscrews 27 acting in the slots 21 of mounting plate 11 and engaged withtapped holes 28 provided in channel member 24. The channel member 24 issecured to the wall, open side in, by fasteners 23 as described inconnection with FIG. 2. In this way the microphone will be in closevibratory contact with the wall through the channel member 24 andfasteners 23.

The overall layout and spacing of the microphones is of course dictatedby the requirements of the particular installation and it is seldom thattwo are ever alike. Nevertheless there are several basic rules, asfollows, which should be observed to provide adequate protection for abuilding block construction vault.

l. The strips carrying the detectors (microphones) should not be spacedat greater than 3 foot intervals.

2. The upper and lower microphone strips should not be spaced more than1 feet from the ceiling and floor, respectively.

3. The spacing between detectors on any strip should not exceed 20 feet.

4. The strip should be fastened to the wall at intervals not exceeding 3feet.

5. The spacing between detectors on the floor and ceiling should notexceed 20 feet.

A typical installation will now be described in conjunction with FIG. 4which is a folded out diagram of a block construction vault measuringfeet in length by 16 feet in width and 9 feet high. The microphones areindicated by M and the microphone strips by S. As indicated, on three ofthe walls, the microphone strips S are located 1% feet from the floorand ceiling and a third strip is added therebetween to maintain thedesired 3 foot spacing between strips. The strips need not be installedhorizontally as shown since a vertical pattern may be more convenient insome cases, as for instance on the front wall on either side of thedoor. it should be noted that an extra microphone is mounted on the doorframe for additional security. The microphones on the other three wallsare shown mounted vertically one above the other primarily forconvenience in making the installation. A staggered pattern may be usedto equal advantage provided that the spacing between detectors on eachstrip does not exceed about 20 feet. At the comers of the vault, thestripping may be bent into a right angle although it will usually bemore convenient to simply start a new strip.

As the floor and ceiling walls will usually be of poured concrete andthus monolithic in nature, stripping will not ordinarily be required; itbeing only necessary not to exceed the limitation of 20 feet betweendetectors. The floor and ceiling wall microphones should be flushed intoa recess cut in the concrete and then grouted with a suitable cementsuch as an epoxy adhesive. it will be noted in FIG. 4 that the floor andceiling microphones are located near the walls. The reason therefor isto avoid the need for running the cable across the exposed surface to acentrally located microphone: In the case of very large vaults, so doingwould be unavoidable to maintain the desired 20 foot spacing.

While the invention has been described in connection with specificembodimentsthereof and in specific configurations, various modificationsthereof will occur to those skilled in the art without departing fromthe spirit and scope of the of as set forth in the appended claims.

What is claimed is:

1. An electrical protection system for detecting physical attacks onvaults and like structures constructed of building blocks of the typewherein a sensor responsive to vibrations in the structure activates anelectronic detecting and alarm device wherein the improvement comprises:

a. a plurality of elongated, metallic, vibratory energy collecting andtransmitting strips each disposed in close physical contact with arespective portion of an interior surface of a select wall of thestructure, each strip being made of a hard metal having a bettervibratory energy conductance than the walls of the structure;

b. at least one vibration sensitive microphone mounted in closevibratory contact with both the interior surface of the select wall andthe strips and being arranged to produce an electrical signal voltage inresponse to detection of vibrations transferred thereto along all axesfrom the select wall and the strips;

c. vibration transmitting mounting means mounting the strips on theinterior surface of the select wall, the mounting means includingindividual metallic attaching elements spaced apart along the strips,penetrating the select wall and contacting the strips to transfervibrations along all axes from the select wall the the strips; and

d. means for supplying the electrical signal voltage from each of themicrophones to the electronic detecting and alarm device.

2. An electronic protection system for vaults and like structuressubject to physical attacks, comprising:

a. a plurality of vibration sensitive microphones mounted in closevibratory contact with the walls of the structure at spaced apartpositions on the interior surfaces of the walls, each of the microphonesbeing capable of producing an electrical signal voltage in response todetection of vibrations transferred thereto along all axes from thewalls of the structure;

b. means for separately collecting vibratory energy along all axes fromnumerous spaced apart positions on the interior surfaces of the wallsand for transmitting the collected vibratory energy from selected groupsof the positions to selected corresponding ones of the microphones, thecollected vibratory energy from the positions in each of the selectedgroups being transmitted as a unit to the selected correspondingmicrophone along an individual transmission path having a sonic energyconductance much greater than the conductance of the walls; and

c. means for detecting the electrical signal voltage output of one ormore of the microphones as an alarm signal indication of an attack on awall of the structure.

3. The method of protecting vaults and like structures subject tophysical attacks, comprising the steps of:

a. positioning a plurality of vibration sensitive microphones in closevibratory contact with the walls of said structure at spaced apartpositions on the interior surfaces of said walls, each of saidmicrophones being arranged to produce an electrical signal voltage inresponse to detection of vibrations transferred thereto along all axesfrom the walls of said structure;

b. separately collecting vibratory energy along all axes from numerousspaced-apart positions on the interior surfaces of said walls;

c. transmitting said collected vibratory energy from selected groups ofsaid positions to selected corresponding ones of said microphones, saidcollected vibratory energy from the positions in each of said groupsbeing transmitted as a unit to the corresponding microphone along anindividual transmission path having a sonic energy conductance muchgreater than the conductance of said walls; and

d. detecting the electrical signal voltage output of one or more of saidmicrophones as an alarm signal indication of an attack on a wall of saidstructure.

4. An electrical protection system for detectingphysical attacks onvaults and like structures having walls subject to physical attack,comprising:

a. an electronic detecting and alarm device;

b. a plurality of vibration-sensitive microphones each mounted in closephysical contact with the interior surface of a wall of said structuresuch that vibrations of said wall surface along all axes are physicallytransmitted to each of said microphones and each of said microphonesbeing arranged to produce an electrical signal voltage in response todetection of vibrations transferred thereto from the interior surface ofa wall of said structure;

c. a plurality of elongated metallic vibratory energy transmittingstrips each extending along and in close proximity to a respectiveportion of a wall surface of said structure and each being in closevibratory contact with select ones of said microphones to aid incollecting and transmitting vibratory energy arising in said respectiveportion of a wall surface to said select ones of said microphones;

d. means including individual metallic mounting elements eachpenetrating a select strip and a wall of said structure for mountingeach of said strips on said respective portion of a wall surface suchthat vibrations of said wall surface along all axes are transmitted toeach strip; and

. means for supplying the electrical signal voltage from each of saidmicrophones to said electronic detecting and alarm device.

5. An electrical protection system as set forth in claim 1 in which saidmicrophones are responsive to a frequency range of about 7,000 to 50,000cycles per second.

6. An electrical protection system as set forth in claim 1 in which saidindividual mounting elements are spaced along said strips at spacingsnot exceeding about 3 feet.

7. An electrical protection system as set forth in claim 1 in which saidmicrophones are mounted on respective sound transmitting metal platesand in which each of said metal plates is attached to a wall of saidstructure by sound transmitting metallic fastening elements capable oftransmitting vibrators in said wall along all axes to said plates.

8. An electrical protection system as set forth in claim 1 in which saidstrips are steel channels having the open sides thereof facing theadjacent structure wall.

9. An electrical protection system as set forth in claim 1 in which atleast some of said microphones are mounted directly on respective onesof said strips.

10. An electrical protection system as set forth in claim 1 in whichsome of said strips are mounted horizontally on each vertical wall ofsaid structure, the strips on each of said vertical walls being disposedgenerally parallel to each other, the strips nearest the ceiling andfloor of said structure being spaced not more than about 1% feet fromthe adjacent ceiling and floor, respectively fatcnt No.

Inventor(s) Charles D. Ott

Dated November 2, 1971 It is certified that error appears in theabove-identified pal tent that said 1, line and line line line line

line

line

7, line 7, line Signed (SEAL) Attest:

EDWARD MQFLETCHERT .TB.

Letters Patent are-hereby corrected as shown below: 57 "preformed"should be pre-formed 9 "systems' should be system l 5 "serve" should besecure 35 after "the" {secon occurrence) insert I invention 35 delete"of" (second occurrence) 61 the" Second occurrence should be to 64 "1"should-be 4 67 "l" shol ld be 4 70 "1" should be 4 l "1" should be -4 4-'"l" should be 4 7 "1" should be --'4 and sealed this 27th day of June1 972 Attest-ing Officer HOBE'JRP GOTTSCHALK Commissioner of Patents

1. An electrical protection system for detecting physical attacks onvaults and like structures constructed of building blocks of the typewherein a sensor responsive to vibrations in the structure activates anelectronic detecting and alarm device wherein the improvement comprises:a. a pluRality of elongated, metallic, vibratory energy collecting andtransmitting strips each disposed in close physical contact with arespective portion of an interior surface of a select wall of thestructure, each strip being made of a hard metal having a bettervibratory energy conductance than the walls of the structure; b. atleast one vibration sensitive microphone mounted in close vibratorycontact with both the interior surface of the select wall and the stripsand being arranged to produce an electrical signal voltage in responseto detection of vibrations transferred thereto along all axes from theselect wall and the strips; c. vibration transmitting mounting meansmounting the strips on the interior surface of the select wall, themounting means including individual metallic attaching elements spacedapart along the strips, penetrating the select wall and contacting thestrips to transfer vibrations along all axes from the select wall thethe strips; and d. means for supplying the electrical signal voltagefrom each of the microphones to the electronic detecting and alarmdevice.
 2. An electronic protection system for vaults and likestructures subject to physical attacks, comprising: a. a plurality ofvibration sensitive microphones mounted in close vibratory contact withthe walls of the structure at spaced apart positions on the interiorsurfaces of the walls, each of the microphones being capable ofproducing an electrical signal voltage in response to detection ofvibrations transferred thereto along all axes from the walls of thestructure; b. means for separately collecting vibratory energy along allaxes from numerous spaced apart positions on the interior surfaces ofthe walls and for transmitting the collected vibratory energy fromselected groups of the positions to selected corresponding ones of themicrophones, the collected vibratory energy from the positions in eachof the selected groups being transmitted as a unit to the selectedcorresponding microphone along an individual transmission path having asonic energy conductance much greater than the conductance of the walls;and c. means for detecting the electrical signal voltage output of oneor more of the microphones as an alarm signal indication of an attack ona wall of the structure.
 3. The method of protecting vaults and likestructures subject to physical attacks, comprising the steps of: a.positioning a plurality of vibration sensitive microphones in closevibratory contact with the walls of said structure at spaced apartpositions on the interior surfaces of said walls, each of saidmicrophones being arranged to produce an electrical signal voltage inresponse to detection of vibrations transferred thereto along all axesfrom the walls of said structure; b. separately collecting vibratoryenergy along all axes from numerous spaced-apart positions on theinterior surfaces of said walls; c. transmitting said collectedvibratory energy from selected groups of said positions to selectedcorresponding ones of said microphones, said collected vibratory energyfrom the positions in each of said groups being transmitted as a unit tothe corresponding microphone along an individual transmission pathhaving a sonic energy conductance much greater than the conductance ofsaid walls; and d. detecting the electrical signal voltage output of oneor more of said microphones as an alarm signal indication of an attackon a wall of said structure.
 4. An electrical protection system fordetecting physical attacks on vaults and like structures having wallssubject to physical attack, comprising: a. an electronic detecting andalarm device; b. a plurality of vibration-sensitive microphones eachmounted in close physical contact with the interior surface of a wall ofsaid structure such that vibrations of said wall surface along all axesare physically transmitted to each of said microphones and each of saidmicrophones being arranGed to produce an electrical signal voltage inresponse to detection of vibrations transferred thereto from theinterior surface of a wall of said structure; c. a plurality ofelongated metallic vibratory energy transmitting strips each extendingalong and in close proximity to a respective portion of a wall surfaceof said structure and each being in close vibratory contact with selectones of said microphones to aid in collecting and transmitting vibratoryenergy arising in said respective portion of a wall surface to saidselect ones of said microphones; d. means including individual metallicmounting elements each penetrating a select strip and a wall of saidstructure for mounting each of said strips on said respective portion ofa wall surface such that vibrations of said wall surface along all axesare transmitted to each strip; and e. means for supplying the electricalsignal voltage from each of said microphones to said electronicdetecting and alarm device.
 5. An electrical protection system as setforth in claim 1 in which said microphones are responsive to a frequencyrange of about 7,000 to 50,000 cycles per second.
 6. An electricalprotection system as set forth in claim 1 in which said individualmounting elements are spaced along said strips at spacings not exceedingabout 3 feet.
 7. An electrical protection system as set forth in claim 1in which said microphones are mounted on respective sound transmittingmetal plates and in which each of said metal plates is attached to awall of said structure by sound transmitting metallic fastening elementscapable of transmitting vibrators in said wall along all axes to saidplates.
 8. An electrical protection system as set forth in claim 1 inwhich said strips are steel channels having the open sides thereoffacing the adjacent structure wall.
 9. An electrical protection systemas set forth in claim 1 in which at least some of said microphones aremounted directly on respective ones of said strips.
 10. An electricalprotection system as set forth in claim 1 in which some of said stripsare mounted horizontally on each vertical wall of said structure, thestrips on each of said vertical walls being disposed generally parallelto each other, the strips nearest the ceiling and floor of saidstructure being spaced not more than about 1 1/2 feet from the adjacentceiling and floor, respectively.